Transfer RNA (or abbreviated as tRNA) is small RNA molecule, typically between 70 to 90 nucleotides in length, which main function is to deliver amino acids required for the process of protein synthesis. tRNAs are carrying amino acids to the ribosome, where the actual protein synthesis takes place. The molecule is directed by the corresponding codon (a three-nucleotide sequence) in a messenger RNA (mRNA). This defines the role of the tRNA as a required component of protein translation. The process of protein translation defines the production of new proteins according to the genetic information. All transport RNA molecules have similar structures because they all interact with the one and the same sites on the ribosome in a similar way.
The order of the nucleotides in messenger RNA determines which amino acids and in what order will incorporated into the protein product of the gene. The role of tRNA is to recognize a specific codon and to deliver the corresponding amino acid (the codon to anti-codon matching pattern). A region within the 3D dimensional structure of the tRNA has a three-nucleotide sequence called the anticodon, which matches the genetic code of the mRNA codon. During the process of protein synthesis, mRNA anticodons bind to the codon of the mRNA and form temporary three base pairs structures. The polypeptide sequence of a protein is encoded by the corresponding mRNA in terms of a series of contiguous codons. Each codon is recognized by a particular type of transport RNA. Each tRNA is covalently bound to the amino acid that corresponds to the anticodon. Each tRNA molecule type can carry just one type of amino acid. So within the cell there are many types of tRNA. On the other hand there are many tRNA molecules which can recognize different anticodons which also carry the same amino acid. This is defined by the fact that for each amino acid (around 20 in the different amino acids) there are multiple codons (of all 64 codons) that defines them.
The amino acid is covalently attachment to the 3′ end of the tRNA 3’ by enzymes called aminoacyl-tRNA synthetases. Usually the cell has a different synthetase for each amino acid. There are specific proteins called elongation factors, which during protein synthesis deliver the tRNAs with attached amino acids are to the ribosome. When the anticodon of the tRNA matches the codon of the mRNA, another tRNA already bound to the ribosome interacts with the 3′ end of the growing polypeptide sequence in a reaction catalyzed by the ribosome.